The invention relates to a method and apparatus for feeding items such as mail pieces into a sorting system, which system includes subsystems for singulation of mail pieces such as parcels.
In high volume product handling operations, such as mail handling and similar processing, large quantities of items such as boxes, parcels packages or parts often varying widely in size, must be inducted into a sorter systems. Typically, a feeder system for use in such processing areas takes a disordered stream of items fed to it on a conveyor and inducts the items onto a sorter system. The feeder system ideally should perform several functions. To the maximum extent possible, the feeder should singulate disordered items in order to present the articles to downstream processing equipment, such as a sorter, one at a time with a minimum specified spacing or separation between product items. The feeder system must also read destination information from the item so that the control system for the sort can track it through the system and sort it correctly. In the U.S., scannable bar codes are used for this purpose. A third important function is intercepting and removing items which are non-machinable because they are too large, too heavy or the like from the system for special handling.
Singulation is an essential first step in the handling and sorting product items such as boxes, parcels or soft packages. Singulation is a process whereby a randomly input stream of items moving on a conveyor system is separated into a stream of single items spaced from each other so that an downstream process can readily perform operations on each item one at a time. Mixed item streams are a particular challenge in that a mixed material stream may include packages that vary greatly in size and may be piled at random one upon another, forming agglomerates of packages that are difficult to detect and separate.
According to one previously proposed method for singulation of mail, an inclined ramp with holes for applying suction is provided. Letters are allowed to slide down the ramp and then suction is applied to hold them in place on the slide. The suction is then selectively released in order to release one item at a time. See Interim Report For Phase I, U.S. Postal Service Contract 104230-85-H-0002, Apr. 5, 1985, ElectroCom Automation, Inc., pages 3-10 to 3-13. This method provides one form of singulation, but is of doubtful utility for larger items that may be difficult to hold effectively using suction and that may tend to tumble down a slide, possibly evading the effect of suction and leaving the singulator prematurely. The system according to the present invention addresses these difficulties.
The invention further provides a variety of innovations useful in sorting system as described in the summary and detailed description which follow.
In accordance with one aspect of the invention, a system for feeding items to a sorter includes a first conveyor that conveys a stream of items to be sorted, a mechanical singulator that receives the stream of items from the conveyor and singulates the items, an automated system for detection and removal from the stream items which exceed predetermined physical limitations associated with the sorter, a scanner for reading destination indicia on each item, a second conveyor for conveying each item for induction to the sorter, and optionally a labeler that labels each item with a label readable by the sorter, which label identifies a sorting destination that corresponds to the read destination indicia.
Such a system in accordance with one embodiment of the invention includes a first singulator section having an infeed end that receives a disordered stream of non-flat, three-dimensional articles, at least one conveyor, and a system associated with the conveyor for mechanically increasing spacing between the articles moving along the conveyor without need to track positions of individual articles on the conveyor. A second singulator section includes at least one conveyor, a detection system that identifies individual articles as each passes through the second singulator section, and a control system that selectively actuates portions of the conveyor of the second section in response to position data from the detection system to remove articles from the second singulator one at a time.
An article sorting method for feeding items to a sorter according to the invention comprises the steps of conveying a stream of items such as mail pieces on a conveyor to an automated singulator, singulating the items using the singulator, detecting and removing from the stream items which exceed predetermined physical limitations associated with the sorter, reading destination indicia on each item, and conveying each item for induction to the sorter for sorting in accordance with the read destination indicia. Each item may further be labeled with a label readable by the sorter, which label identifies a sorting destination that corresponds to the read destination indicia.
In another aspect, the invention comprises a singulation system including a first singulator section having an infeed end that receives a disordered stream of non-flat, three-dimensional articles, at least one conveyor, and a system associated with the conveyor for mechanically increasing spacing between the articles moving along the conveyor without need to track positions of individual articles on the conveyor. A second singulator section receives the stream of articles from the first singulator section, the second section including at least one conveyor and a detection system that identifies individual articles as the articles pass through the second singulator section. A control system selectively actuates portions of the conveyor of the second section in response to position data from the detection system in a manner effective to remove articles from the second singulator one at a time. The first singulator section may include first and second conveyors disposed end to end so that articles leaving the first conveyor are received by the second conveyor, the second conveyor moving at a greater speed than the first conveyor.
Such a two-stage singulation process may be characterized as successive coarse and fine singulation operations that improve singulation efficiency. For purposes of the present invention, xe2x80x9ccoarsexe2x80x9d singulation refers to a mechanical process which tends to singulate a disordered stream of items by attenuation of the stream (increase in spacing between items) but which does not track items individually. xe2x80x9cFinexe2x80x9d singulation refers to a process wherein individual items traversing the singulator are identified and/or tracked with a detection system such as a vision system, and controls are used to affect the stream in a manner that ensures or at least promotes singulation, for example, by diverting items back to ensure delivery of items from the system one at a time. Thus, a fine singulating step includes monitoring individual items traversing the system. Spacing of items in the disordered stream may be monitored with a detection system such as a vision system, and input from the vision system is used to control the system and to promote separation of items into an ordered one-by-one stream. The vision system may be used to identify and track individual items passing through the system.
Successive coarse and fine singulation operations are particularly useful for recycling and separating xe2x80x9cdoublesxe2x80x9d or xe2x80x9cmultiples,xe2x80x9d namely two or more items in continuous material stream that are overlapping, side-by-side or consecutive without sufficient spacing. For this purpose, the coarse singulation step or section may fiter include a step of dropping items off of one conveyor and onto another in a manner that would tend to break up doubles, but of sufficiently short distance that damage to the items is minimal.
Thus, the invention provides a method of singulating a group of items includes the steps of introducing a disordered stream of items onto a coarse singulator which mechanically tends to increase spacing between items in the stream, and then passing the stream to a fine singulator wherein individual items are tracked with a detection system and controls are used to affect the stream in a manner that promotes singulation. As described in detail herein, the xe2x80x9cfinexe2x80x9d singulation may be accomplished with a chevron, hold-and-release or longitudinal strip conveyor. Alternatively, xe2x80x9ccoarsexe2x80x9d singulation may be accomplished with a series of cascaded, e.g., ramped conveyors which, in one embodiment, may be angled in a horizontal plane relative to the preceding and/or succeeding conveyor. In one embodiment, one or more inclined conveyors comprising independently driven longitudinal conveying sections, such as parallel strip belts may be used for coarse singulation or, with the addition of a vision system and intelligent control, may be utilized for fine singulation.
In one embodiment, a coarse singulator includes at least one inclined conveyor, disposed at an angle of from about 5xc2x0 to about 30xc2x0, for receiving a stream of articles to be singulated, including a lower article receiving area and upper article discharge end. A succeeding conveyor, preferably operated at a higher speed than the preceding conveyor, receives articles or items dropping from the discharge end of the preceding inclined conveyor. In one embodiment, one or more of the conveyors is positioned at an angle in the horizontal plane relative to the preceding conveyor at an angle from about 5xc2x0 to about 90xc2x0 to further promote singulation. The transfer process over the cascaded conveyors tends to break up or separate multiples or clusters of items and effect is increased if the succeeding conveyor is operated at a higher speed.
In another aspect, a coarse or fine singulating chevron-type conveyor includes a first conveyor section set at a first horizontal angle relative to a lengthwise conveying direction of the conveyor, and a second conveyor section set at a second horizontal angle relative to a lengthwise conveying direction of the conveyor. The first and second sections each extend in the lengthwise conveying direction of the conveyor and are positioned to cause items traveling on either section to move towards a central lengthwise axis of the conveyor while moving in the conveying direction of the conveyor. A control system may be provided for selectively operating the first and second conveyor sections in a manner that promotes singulation of items. In a preferred form, the first and second conveyor sections comprise groups of angled rollers, angled of from about 5xc2x0 to 85xc2x0 relative to a central axis of the conveyor. The rollers of the first and second conveyor sections each have separate drive systems whereby rollers of the first section can operate independently of rollers of the second section, and most preferably, subgroups of rollers within each section each have separate drive systems. At least one sensor, such as a digital camera may be provided to monitor the density of articles at one or more points in the system. Images captured by the camera may in turn be used to regulate the speed of one or more of the conveyors.
The invention further provides a recirculating singulation system. In this system, a conveyor conveys a stream of incoming items to a mechanical singulator that receives the stream of items from the conveyor and singulates the items. An automated system is provided for detecting insufficient spacing between items in the stream of items from the singulator. This system includes a controller for operating a divert mechanism that diverts an item identified by the automated detection system back to the stream of items on the conveyor for incoming items. An edging divert conveyor of the invention is a preferred form of divert mechanism for use in a recirculation loop. Such a divert mechanism includes an edger conveyor having angled rollers which convey items along a gate at one side of the edger conveyor. A return path such as a slide or chute leads from the gate to a conveyor for incoming items, or other destination. A control mechanism opens the gate to divert an item identified by the automated detection system for diversion, for example, along the return path back to the stream of items on the conveyor for incoming items. The recirculation loop may include a coarse singulation system only, a fine singulation system only, or both in series as described in the detailed description which follows.